Different feature-based positioning methods for mobile users or terminal devices in wireless communication networks are known from the prior art. In this situation, the field strengths of fields through the mobile object for example are measured as features, whereby the field is generated and emitted by a plurality of base stations in the communication network. DECT networks (DECT=Digital Enhanced Cordless Telecommunication), WLAN networks (WLAN=Wireless Local Area Network) and the GSM (GSM=Global System for Mobile Communication) and UMTS (UMTS=Universal Mobile Telecommunication System) mobile radio networks are for example employed as communication networks.
So-called reference maps in which a relationship between the spatial position of the node and feature-dependent variables of the individual base stations is stored for a plurality of nodes are frequently employed with regard to the feature-based positioning. Feature-dependent variables in a field strength based method for example are the field strength of the field emitted by a base station at the spatial position of the node or the field strength, measured at the base station, of a field which is emitted by an object which is situated at the spatial position of the node. As a result of measuring the field strength at any desired position and comparing the measured value with the field strength dependent variables at the nodes of the reference map it is possible to ascertain the position of the object.
Different methods for the feature-based positioning with the aid of reference maps are known from the prior art. In conventional methods, in this situation a calibration or initial measurement of reference patterns for producing the reference map is first performed in order to achieve a sufficient degree of accuracy in structured environments. The positioning is then performed on the basis of the reference map ascertained in this manner.
Positioning methods are moreover known wherein an initial calibration of the reference map is dispensed with. Such a positioning method is described in the publication DE 10 2006 044 293 A1. In this method, parallel to the positioning the nodes of a reference map are also simultaneously learned stepwise on the basis of the measured features of the field.
In this situation, the method commences with a coarse initialization of the reference map which for example is based on a linear radial model of the radiation propagation of the base stations.
In order to avoid any error propagation in the methods described above for the positioning of an object or for learning a reference map, it is necessary to ensure with regard to the positioning or the learning of the reference map that the object is moving only in a predetermined region provided for the positioning. This serves to avoid measurements which are situated outside the predetermined region being assigned to this region and thus resulting in a corruption of the positioning or of the learned reference map. There is however also a need to enable a positioning or a learning of a reference map for an object moving randomly in the area surrounding the predetermined region, such that it is not necessary to ensure that the object is also always situated in the predetermined region. In such a case a suitable method must be created which makes it possible to determine whether the object is situated inside or outside the region of the reference map.